1. Field of the Invention
This invention relates to the making of air bridges using multi-level photoresist and metallization in lieu of any electro-plating method.
2. Prior Art
Millimeter wave (mmW) and monolithic Microwave Integrated Circuits (MMIC) incorporate HBT (heterojunction bipolar transistor) and HEMT (high electron mobility transistor) devices which require low capacitance, low inductance, high Q air bridge interconnections, not available heretofore.
Prior art air bridges are fabricated using electro-plating procedures. They require multiple photoresist applications and plating media metallization. The plating media must be removed following the plating process.
These procedures are time consuming and subject the circuits to be processed to harsh chemical plating and chemical etching environments which can damage delicate devices.
In addition, plated gold, which is the plating metal used for air bridges, has low conductivity, necessitating thick metal thicknesses to insure high quality crossovers.